Competency 046:Structure and Function of Living Things

The teacher understands the structure and function of living things.

With millions of different kinds of organisms in the world, scientists must find order in all of this diversity. Scientists group living organisms into one or more of a few major categories as part discipline known as taxonomy. The bodies of organisms are organized into functional systems—cells are organized into tissues, and tissues are organized into organs. Body systems carry out critical functions, such as locomotion, reproduction, digestion, and circulation. All living things on Earth are composed of the same carbon-based, molecular building blocks.

Characteristics of Organisms from Major Taxonomic Groups

The beginning teacher describes characteristics of organisms from the major taxonomic groups.

Key Concepts:

Modern taxonomy, using molecular analyses, divides all living organisms into three domains: Bacteria (includes the Kingdom Eubacteria), Archaea (includes the Kingdom Archaebacteria), and Eukarya (includes the Kingdoms Protista, Fungi, Plantae, and Animalia).

The hierarchical system of classification originally conceived by Linnaeus includes seven levels or taxons. These levels are kingdom, phylum, class, order, family, genus, and species; representing general to specific organism attributes.

Species names of organisms always are written as two words, consisting of the genus and species designation.

Resources:

Classifying Living Things. Dr. Michael McDarby explains how living organisms are classified as part of the Online Introduction to the Biology of Animals and Plants

The Three Domain System. Dr. Gary Kaiser compares the three domains of cellular organisms: Archaea, Bacteria (Eubacteria) and Eukarya.

Domains. Mary Poffenroth explains the three biological domains in this presenation from Mahalo Biology.

The Taxonomic Hierarchy. Mary Poffenroth looks at the biological classification system in a video from Mahalo Biology.

How Structure Complements Function in Cells

The beginning teacher analyzes how structure complements function in cells.

Key Concepts:

All organisms are composed of cells. Organisms can be single-celled or multicellular.

In multicellular organisms, the shape of the cell helps determine its function. For example, red blood cells are donut-shaped to easily exchange oxygen and freely pass through narrow blood vessels while nerve cells are long so when connected to other nerve cells they can span long distances in the organism.

Modern cell theory states that all organisms are composed of one or more cells; cells are the basic units of all organisms; and cells arise only through division of a previously existing cell.

All cells have three major features: a nucleoid or nucleus (central portion of the cell containing genetic material), cytoplasm (semifluid matrix or gel, which fills the interior of the cell), and plasma membrane (phospholipid bilayer embedded with proteins surrounding the cell).

Prokaryotes are the simplest organisms. There are two main types of prokaryotes: archaebacteria and bacteria. Most prokaryotes have a strong cell wall outside of the plasma membrane. The internal organization of prokaryotic cells is simple, with few internal compartments and no subunits (organelles surrounded by a membrane). Prokaryotic cells do not have a true nucleus surrounded by a membrane. Instead, their genetic material is present as a simple circle of DNA.

Eukaryotes, which comprise the Domain, Eukarya, contain membrane-bounded organelles that carry out specialized functions and a nucleus that is surrounded by a double membrane (nuclear envelope). DNA inside the nucleus is organized into chromosomes.

Resources:

View the following videos to get a better understanding of size and shape of cells as it relates to their specific function.

Human Body Systems and their Functions

Key Concepts:

Organization of the body’s cells into specialized tissues, organs, and organ systems helps create a division of labor in the body and makes multicellular life possible.

The human body has several organ systems. These systems include the skeletal, muscular, circulatory/cardiovascular, nervous/sensory, respiratory, digestive, excretory, endocrine, reproductive, and immune/lymphatic.

Resources:

Basic Anatomy: Tissues & Organs. Read this web page for a quick overview of the body systems, including organs, and the major role of each.

Animal Tissues and Organs. To review organ systems and their functions, select the appropriate links on this site to watch a short video.

Human Body Systems. These slides and notes provide an overview of tissues in the human body.

How Organisms Obtain and Use Energy and Matter

The beginning teacher describes how organisms obtain and use energy and matter.

Key Concepts:

All living organisms depend on a source of energy to survive.

Energy is the ability to perform work.

Adenine triphosphate (ATP) is the chemical that stores and releases energy to drive reactions in each cell.

Autotrophs (e.g. plants) use light energy from the sun to produce chemical energy (stored as chemical bonds in glucose) and ultimately structural components for the body of the organism, as well as energy for work.

Producing chemical energy from the light energy (electromagnetic radiation) is called photosynthesis.

Structure and Function of Basic Chemical Components of Living Things

The beginning teacher applies chemical principles to describe the structure and function of the basic chemical components (e.g. proteins, carbohydrates, lipids, nucleic acids) of living things.

Key Concepts:

All living organisms on earth are made up of chemicals based mostly on the element carbon. Carbon can form covalent bonds with up to four atoms. This characteristic allows carbon to form many diverse molecules.

Most biological molecules consist of carbon atoms bonded to other carbon atoms or to atoms of oxygen, nitrogen, sulfur or hydrogen. Molecules containing carbon can form chains, branches or rings.

Some biological molecules, such as sugars, are relatively small. Other biological molecules are large and complex, and are referred to as macromolecules. In many cases, the macromolecules are polymers, which are long chains of similar, linked subunits. Complex carbohydrates, such as starch, proteins and nucleic acids all are polymers.

Carbohydrates store energy and provide building materials. Carbohydrates are a large group of molecules that contain carbon, hydrogen and oxygen. Simple sugars (monosaccharides) such as glucose, double sugars (disaccharides) such as sucrose and lactose, and starches (polysaccharides) are carbohydrates.

Lipids (fats and oils) make up membranes and store energy. Lipids will not dissolve in water. Lipids have long sections of non-polar carbon-hydrogen bonds. When placed in water, lipid molecules form clusters with any polar sections facing toward the exterior and non-polar portions toward the interior (away from water). Lipids include triglycerides (dense energy storage formed in fat cells), phospholipids (structural component of the cell membrane phospholipid bilayer), steroids (e.g. cholesterol), and waxes (waterproofing).

Proteins perform the chemistry of cells. Proteins consist of chains of amino acids that may interact and fold over each other to form different shapes and structures. Protein functions include structural support, enzymes for reactions, transport of other molecules, storage, signaling, movement in the organism, and immune defense.

Nucleic acids store and transfer genetic information. Nucleic acids are composed of a sugar, a phosphate group, and a nitrogen base. The two major types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA and RNA sequences are a code for the inherited traits of an organism.

Resources:

The following short videos describe the structures and functions of the basic chemical components of cells.